Development of Ovonic rechargeable metal hydride batteries

Research work in the areas of hydrogen evolution, oxidation, and storage, which culminated in the development of Ni-metal hydride batteries, is described. Initial work on the thin-film materials for hydrogen oxidation in fuel cells and for hydrogen storage in the dry phase led to the development of thin-film hydrogen storage materials suitable for battery use. The composition range of interest for obtaining maximum hydrogen storage capacity with a good chemical stability was studied. Techniques for bulk preparation of hydrogen storage materials and for fabricating these materials into viable electrodes were developed. Cells using modified-alloy negative electrodes showed better self-discharge and rate behaviour, but the internal cell pressure reached unacceptable levels. The origin of the pressure increase was traced to oxide layers on the negative electrode, and techniques were developed for removing these oxide layers first externally and then in situ. Some of the performance characteristics of the batteries are discussed